The present invention relates to fume hoods of the type which are used in science labs for schools. Fume hoods of this type, of course, are well-known and have been used in science laboratories for many years. Most of the prior fume hoods have been adapted to be mounted or placed against a vertical wall so that access or use of the hood was gained primarily through one side of the hood. Further, an instructor, in the case of a hood mounted flush against the wall, normally was constrained to a location behind the student, and could not readily view a student's work within the hood.
Another problem with fume hoods of the type with which the present invention is concerned is that of adapting the hood system to different types of exhaust. Typically, a fume hood is exhausted through a ceiling (called an updraft exhaust), and in the past, most systems have been designed for this primary type of exhaust. However, there are circumstances in which it is desired to exhaust the fume hood through a floor or downwardly (called a down-draft exhaust). In the past, special baffling and re-routing of exhaust conduits were required in order to convert an up-draft exhaust system to one having a down-draft exhaust.
Briefly, the fume hood of the present invention includes a base having a work top of polygonal shape, preferably octagonal. The sides of the hexagonal shape are alternately relatively long and relatively short, the longer sides providing the work areas. A plenum having the same horizontal cross section as the base is located above the base and provides the top of the fume hood. The plenum is supported by a tubular column which extends between the centers of the base and plenum.
Transparent viewing screens extend between the shorter sides respectively between the lower base and upper plenum to separate the work areas while permitting an instructor to view the entire interior of the fume hood from a single location. Eye-screens, including a movable baffle are located above the work areas, the baffle being provided to adjust the velocity of intake air, if desired.
The lower portion of the tubular column is apertured for drawing in heavier-than-air gases within the hood, and the lower side of the plenum includes slots located above the respective work areas for drawing in lighter-than-air gases. In an up-draft exhaust hood, the gases entering at the lower portion of the tubular column are drawn upwardly and combined with the gases in the plenum for exhaust through an upper discharge conduit. In a downdraft exhaust hood, the plenum gases are routed downwardly through the central tubular column where they are combined with the lighter-than-air gases, and both are exhausted through a lower discharge conduit extending through a central pedestal upon which the fume hood is mounted.
Plumbing and electrical conduits are also routed from the floor through the central pedestal to the base of the hood so that they are hidden from view. Overhead lights may also be mounted in the plenum for providing interior light, with the conduits being routed from the base to the plenum through the tubular column.
With the present invention, it has been found that the face velocity of room air through the work openings is quite uniform throughout the entire work opening, whether the fume hood is used with an up-draft exhaust or a downdraft exhaust, and without the need for special baffling or complicated exhaust conduits. Further, the uniform face velocity of room air is achieved whether the movable eyescreens at each work opening are in a raised or a lowered position.
Thus, the present invention provides a laboratory fume hood wherein a number of students may use the hood simultaneously, each having his own work area, but also having convenient access to chemicals or supplies within the hood. At the same time, an instructor may view all that is transpiring in the hood from a single viewing position.
Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment, accompanied by the attached drawing, wherein identical reference numerals will refer to like parts in the various views.